Conventional continuous cigarette rod making machines generally include a feeder and a making apparatus. The feeder showers tobacco material on a rapidly moving paper web which is guided through a rod folder tongue and a paster which seals the paper about the tobacco and forms a continuous rod. The rod then passes through a cut-off wherein a rotating knife blade is driven in a predetermined time relative to the movement of the rod. The cut rods are picked up and delivered to other units for further processing.
There are a number of commercially available, high-speed cigarette makers on the market. Many are capable of making up to about 4,000-5,000 cigarettes a minute. Above this speed, however, it becomes increasingly difficult to provide machinery with moving parts capable of sustained operation. Particularly susceptible to wear are the rotating or reciprocating parts which contact the rod, such as the cutter employed to sever the rod into individual lengths. The high rotational speed required to keep pace with the moving rod is extremely difficult to attain or control. Errors in the precise cutting of the rod rapidly become large as rotational speeds are increased. Additionally, the edge of the rotating blade is quickly eroded and requires constant sharpening.
Cigarettes are generally filled with short shreds of tobacco material. The mass of shreds within the rod is slightly compressed and retains its integrity in part due to entanglement and random orientation of the shreds. At the ends of the rod, integrity is less, thus giving rise to a greater probability of having loose ends. The decreased integrity may result in shreds being lost during further processing or in the fall out of the burning cone during consumer use. High speed cutting of the rod appears to aggravate the problem of loose ends, since many shreds are torn or pulled away from the mass. The ends of the cigarettes are in many instances visually "out-of-the-round" and less dense than other portions of the tobacco column. Not only is the appearance of the tobacco product unappealing to the consumer, but often the delivery of the taste constituents in the smoke is undesirably altered.
Industrial application of the laser is becoming increasingly commonplace. Operations, such as fine welding, cutting, and drilling, have been particularly amenable to the use of the laser, which, in at least one instance, has been used in the manufacture of tobacco products. The laser is particularly useful in the cutting and removal of materials in selected regions because of its ability to generate an intense coherent beam of light, thereby permitting transmission of large amounts of energy in a narrow, substantially nondivergent beam.
The use of a laser, however, has a disadvantage when the laser is being employed with materials which are chemically or physically affected when in the proximity of high temperatures or other materials which suffer deformations due to overheating. Combustible materials, for example, may ignite or char when exposed to a laser beam. As described in U.S. Pat. No. 3,679,863, a laser is employed to cut a combustible workpiece, such as timber, carpet, fabric, and, particularly, paper, which ordinarily results in the charring or deposition of distillates. To prevent combustion, a jet of inert gas carrying an atomized stream of liquid coolant is directed on to the moving region of the workpiece at which the laser beam is concentrated. U.S. Pat. No. 3,629,546 also describes the use of a coolant air stream for similar purposes.
United Kingdom Pat. No. 1,333,867 sets forth a method for cutting a cigarette rod via a deflected laser beam. A laser device produces a beam which is deflected by a mirror system so as to be reciprocated both in line with the rod and across the rod to affect the cutting action. Because discernible charring along the cut edge, particularly the edge of the highly combustible wrapper, is undesirable, the patentee describes a process which introduces an inert gas into the tobacco filler so that the gas is present in the formed cigarette rod where the cigarettes are cut off by the laser beam. The gas is caused to move through the wrapped rod with a force sufficient to expel air from the rod. According to the patentee, the inert gas reduces or eliminates charring at the ends of the cigarettes.
While it must be appreciated that the use of a laser for cutting purposes in the manufacture of cigarettes eliminates speed and efficiency constraints imposed by mechanical cutting, the use of an inert gas or other similar means to reduce combustion and/or act as coolant has significant drawbacks. It requires additional equipment in manufacturing facilities where space is limited. Additionally, directing the flow of an inert gas stream through the rod aggravates the problem of loose ends, since the gas flow adversely affects the integrity of the mass of tobacco shreds. The flow of gas may tend to loosen shreds from the mass, resulting in further waste and in coal fall out. Furthermore, the expense of providing the inert gas renders such a process economically unattractive.
Accordingly, it is an object of the present invention to provide a method by which combustible tobacco materials in rod form can be cut with a laser beam under essentially atmospheric conditions without requiring a coolant means to prevent scorching of the shreds and wrapper.
It is still another object of this invention to provide a method by which shredded combustible tobacco materials in rod form can be cut with a laser beam under the aforementioned condtions and produce cut rods with increased end stability.
Other objects and advantages will be readily evident to those skilled in the art in the light of the following description and appended drawings.